Hard metal body



Patented June 2, 942

2,285,205 HARD METAL BODY Josef Hinniiber, Essen, Germany,

General Electric New York assignor to Company, a corporation of NoDrawing. Application June 8, 1940, Serial In Germany July 24, 1939 2Claims. (Cl. 51,309)

It is well-known practice to secure shaped hard metal bodies tosupporting bodies, which generally consist of tool-steel, by brazing.This method is, however, difiicult of accomplishment if hard metalrings, for example grinding cylinders or the like, i. e. bodies havinga'supporting sectional area that is small in proportion to theirexternal dimensions, are to be secured to the respective supportingbodies. In fact, this method facilitates the development of tensioncracks as a consequence of either the contraction strains set up duringbrazing on account of the diiferent coeflicients of expansion of thesupporting body and the hard metal body, or the bending stresses causedby the cambering of supporting bodies of lesser strength when subjectedto the brazing operation.

Another known method, which consists in connecting hard metal tip to thesupporting shank by forcing the tip against the tool body, underpressure and simultaneous heating of the tip, in cases where it isintended to secure hard metal rings, for example grinding cylinders orthe like,

to supporting members, proves likewise costly, having regard to the useof special moulds, and is not always feasible.

With a view to eliminate such difiiculties, it has already been proposedto make the support from an alloy having a coefficient of expansionapproximately equal to that of the hard metal ring, and to braze thehard metal body onto it.-

The present invention essentially consists in that the supporting memberis made from a-sintered alloy, and that the hard metal body, which may,by way of example, be composed of tungsten carbide, alone or in mixturewith other carbides, as titanium carbide, tantalum carbide, niobiumcarbide, vanadium carbide, and up to 20% auxiliary metal with lowermelting point,

as cobalt, nickel and/or iron, is secured onto it by sintering.

Thus, as an example, the supporting member is produced by pressing amixture of, for example, 38 to 45% nickel, remainder iron, and thensintering it at a temperature of about 1200" C.

Patent is:

1. A tool comprising .a ring-shaped diamond Such sintered plate issurface ground, and the likewise surface ground shaped hard metal bodyis placed upon it. The whole is then once again heated to atemperatureof about 1200 to 1300 C. In cases where recarburization is tobe avoided, it is convenient to effect the heating in a ceramic tube,using hydrogen as a protective as.

Instead of the before-mentioned mixture, one may also start, dependingon the intended use, from pure carbonyl iron, or from aniron-chrometungsten alloy, or from molybdenum, or molybdenum alloys. Itis of advantage to choose for the support an alloy having a coefiicientof expansion that corresponds fully or approximately to that of the hardmetal body.

In some cases where it is important for the hard metal body to lie planeon its supports, the sintering of the supporting member may be performedin one operation with the sintering-on of the shaped hard metal bodies.It is possible to facilitate and accelerate the sintering-on of the hardmetal body by applying a pressure, which may be exerted, for example, bya molybdenum body placed upon it. 1

The sintering-on operation may, if necessary, be further facilitated byinterposing between the support and the hard metal body a pulverulentmixture of an iron-nickel alloy, or of a soft metal, as cobalt or nickel'or the like, in pulveru'lent condition.

The present inventionis of particular interest to the fixing of grindingcylinders that are im-- pregnated with diamond grains and are, owing tothe heterogeneity brought'about by such diamonds, inferior in strengthto the standard harc metal. Such grinding cylinders represent a highvalue, which being fixed so as to eliminate any breakage in order toavoid disintegration in view of the high speeds of rotation being used.1

What I claim and desire to secure by Letters impregnated tool bitsintered to a separately formed sintered supporting shank, said bitconsisting of a hard'metal bodyand said shank consisting of about 38 to45% mainder substantially all iron.

2. A tool comprising a ring-shaped tool bit sintered to a supportingshank, said bit consisting of diamonds distributed through asinteredcomposition consisting of tungsten carbide and metal of the iron group,tered alloy containing about 38 to 45% nickel with the remaindersubstantially all iron.

JOSEF HINNUBER.

is another reason calling for their nickel with the resaid shankconsisting of a sin-

